It is well known to utilize sidepocket mandrels in oil and/or gas wells in which the mandrel has a main bore which is aligned with the production tubing string and also includes an offset bore having a pocket for receiving various types of flow control devices which can be used for various functions such as controlling other equipment or controlling the flow of fluid between the interior and the exterior of the mandrel. As indicated in U.S. Pat. No. 4,333,527, many different types of construction has been utilized in order to increase the strength of the sidepocket mandrels and make the mandrels less subject to failure. However, many mandrels include an orienting sleeve which is positioned in the main bore for guiding and actuating a kickover tool for inserting and removing flow control devices from the sidepocket. It is important that the internal diameter of the orienting sleeve be as great as the internal diameter of the main bore in order not to restrict the passage of well tools through the main bore of a tubing string. The mandrels are threadably connected at each end to the tubing string by threads. So long as the threads are standard types such as EUE, an orienting sleeve may pass through a female thread and be secured into the main bore. However, many of the threads are of the premium type such as sold or licensed by Vam, Mannesmann, or Hydril. These premium threads have a smaller internal diameter and consequently a conventional orienting sleeve cannot be passed through these threads. Therefore it is customary as indicated in U.S. Pat. No. Re. 29,870 and U.S. Pat. No. 4,416,330 to secure the mandrel ends by circumferential welds or by threads to the main mandrel body. That is, generally the ends are formed separately by swaging to provide the necessary thickness for the premium threads, and the orienting sleeve may be inserted into a swage end opposite the thread blanks and secured therein and thereafter the swage may be connected to the main mandrel body, generally by circumferential weld.
However, it is desirable to reduce the number and extent of welds in a mandrel to reduce the possibility of failure. The present invention is directed to a method of forming one end of a mandrel into a tubular shape having an internal diameter large enough to receive an orienting sleeve through the formed end securing the sleeve in the mandrel and reforming the end to a smaller internal diameter to form a premium thread. The present invention is also directed to an integrally forged mandrel having a body and ends made in one piece without any circumferential welds or joints thereby increasing the structure integrity of the mandrel and reducing its exposure to failure.